Background - Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics - page 15

CHAPTER 2
Background

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CONTENTS
2.1 INDEPENDENT AND DEPENDENT VARIABLES

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2.2 TYPES OF DATA 16

2.2.1 Nominal Data 16

2.2.2 Ordinal Data 17

2.2.3 Interval Data 18

2.2.4 Ratio Data 19

2.3 DESCRIPTIVE STATISTICS 19

2.3.1 Measures of Central Tendency 19

2.3.2 Measures of Variability 21

2.3.3 Confidence Intervals 22

2.3.4 Displaying Confidence Intervals as Error Bars 24

2.4 COMPARING MEANS 25

2.4.1 Independent Samples 26

2.4.2 Paired Samples 27

2.4.3 Comparing More Than Two Samples 29

2.5 RELATIONSHIPS BETWEEN VARIABLES 30

2.5.1 Correlations 30

2.6 NONPARAMETRIC TESTS 31

2.6.1 The χ 2 Test 31

2.7 PRESENTING YOUR DATA GRAPHICALLY 32

2.7.1 Column or Bar Graphs 33

2.7.2 Line Graphs 35

2.7.3 Scatterplots 36

2.7.4 Pie or Donut Charts 38

2.7.5 Stacked Bar or Column Graphs 39

2.8 SUMMARY 40

This chapter covers background information about data, statistics, and graphs that
apply to just about any user experience metrics. Specifically, we address the following:

• Thebasic types of variables and data in any user experience study, includ-

ing independent and dependent variables, and nominal, ordinal, inter-
val, and ratio data.